1. Field of the Invention
The present invention relates to a vehicle-use power supply control apparatus suitable for use in a vehicle such as a passenger car, a truck and a bus.
2. Description of Related Art
There is known a vehicle-use power supply control apparatuses which includes an alternator driven by a vehicle engine, a battery, a capacitor parallel-connected to the battery, and a DC/DC converter connected between the capacitor and the battery to enable two-way power transmission therebetween. This vehicle-use power supply control apparatus is configured to supply regenerative power generated by the alternator when the vehicle is decelerating to the capacitor through the DC/DC converter to store the regenerative power on a temporary basis, and discharges this regenerative power through the DC/DC converter when the vehicle is accelerating. This makes it possible to reduce the power generation amount of the alternator, to thereby improve fuel economy of the engine. For more details, refer to Japanese Patent Application Laid-open No. 6-296332, for example.
Meanwhile, the generation voltage of the alternator of such a vehicle-use power supply control apparatus is controlled at a constant voltage by a regulator, while the torque of the alternator varies depending on power consumption of electrical loads operating on power supplied from the battery or the alternator. Accordingly, the conventional vehicle-use power supply control apparatus as described above has a problem in that it cannot efficiently improve the fuel economy of the engine (that is, the fuel economy of the vehicle), because the alternator does not necessarily operate at a desirable power generation torque within a range in which the power generation efficiency of the alternator is high.